Envelope construction



De. 25, 1934. I s MCCULLQUGH 1,985,324

ENVELOPE CONSTRUCE'ION Filed July 16, 1928 structure which may longitudinal sectional view of Patented Dec. 25, 1934 1,985,324 I ENVELOPE CONSTRUQTION Frederick S. McCullough, Edgewood, Pa., assignor to The Union National Bank of Pittsburgh,

Pittsburgh, Pa.

. Application July 16, 1928, Serial'No. 293,201

My invention relates to the construction of vitreous envelopes for vacuum apparatus, and particularly to the construction of substantially cylindricalenvelopes for bodies having transverse extensions projecting laterally through the walls of the envelope. In my co-pending application, Serial No. 286,370, filed June 18, 1928, I have pointed out one method of enclosing suchbodies within such envelopes, and have set forth in detail some of the advantages to be attained thereby. One object of this invention is to provide an alternative method of assembly for structures of the type described therein.

Another object of my invention is to provide a structure whereby the enclosed body may be made in a single piece. I

Another object of my invention is to provide a be formed without special welding equipment. I

Still another object of my invention isto provide a construction in which the glass seals are not subjected to heavy electrostatic stress.

My invention possesses other objects and valuable features, some of which will be set forth in the following description of my invention which is illustrated in the drawing formingpart of the specification. It is to be understood that I do not limit myself to the showing made by the said description and drawing, as Imay adopt varying forms of my invention within claims.

Referring to the drawing, the single figure is a a three electrode relay or audion, constructed in accordance with my invention. a

Broadly stated, my invention comprises a body having transverse extensions adjacent its ends, enclosed Within a vitreous envelope, through the walls of which the ends project. The envelope'is formed in two parts, in each of which is an aperture for one of the extensions. The parts of the envelope are separately placed over the body, passing the extensions through the apertures, and the parts of the envelope are contacted and sealed, the plane of the seal thus intersecting the body between the extensions.

To illustrate my invention, I have chosen for detailed description a space discharge tube em-- bodying it, the tube illustrated being of the power audion type having a water-cooled :electrode. The audioncomprises a coiled axis of the coil, which thus forms a substantially rigid body having transverse extensions adjacent its ends. The ends may be brought out in the the scope of the tubular anode 6 having ends 7 turned outwardly transverse to the same plane, giving the whole member a substantially U shaped form, but this is not an essential feature.

A glass envelope is provided for the coil 6, and is formed from the two preferably co-axial parts 8 and 9, each of which is provided with an aperture to pass one of the extensions '7. For convenience in forming a seal or joint between the extension and the envelope, each of the apertures is provided with a short glass nipple 11 which projects outwardly. x

In assembling the device, the parts 8 and 9 are separately placed over the body 6,-being tilted with respect to the axis of the coil to allow the extensions 7 to be slipped through the nipples 11. The parts of the envelope are then rotated into contact and the seal 12 is formed between them.

Each nipple is then drawn down to form a seal 13 with the sleeve 14, which bridges a groove 16 formed in the extension 7 as is described-in my co-pending application, Serial No. 269,439, filed April 12, 1928.

The grid structure 17, mounted on the end of the closed tube 18 is next inserted through the open end of the envelope, and secured by a seal 19, similar to those just described. A stem 21, carrying a filament structure 22 is then sealed into the other end of the envelope, and the audion is ready to be evacuated and sealed off in a tip 23.

It will be noted that the seal 12 is formed in a plane which intersects the coil 6 between the extensions 7. The audion is designed to have a cooling fluid circulated through the coil, which is thereby maintained at a relatively low temperature. The seal 12 for this reason is not subjected to excessive heat, and it is also shielded by the coil 6 from electron bombardment. 'As a result it does not tend to give off occluded gases and so lower the Vacuum. Being a simple circumferential seal, it is relatively easy to make In my co-pending application, Serial Number 286,370, mentioned above, I have pointed out the advantages of audions of the general form described. The structure here shown has the advantage of having the fluid-cooled electrode 6 formed of a single piece, and hence free from any likelihood of leaks between the coil itself and its projecting extensions or leads 7.

I claim: l

1. The method of forming a. space discharge tube having a glass envelope and a metal coil within the envelope wherein the coil has extensions thereonprojecting outwardly therefrom in a plane substantially perpendicular to the axis of the coil, which comprises forming the envelope 2 in two sections, each having a transverse nipple thereon for the reception of a coil extension, separately fitting each piece about the coil with the respective extensions of the coil passingthrough the nipples of the extensions, and thereafter fusing the sections together and fusing the nipples about the extensions.

2. An electron discharge device comprising a substantially cylindrical glass envelope having electrode supporting means at opposite ends thereof and having electrodes therein supported by the supporting means and a further electrode comprising a coiled tube having outwardly projecting ends, the coil having its axis extending longitudinally of the cylindrical envelope,'said outwardly projecting ends extending transversely to the axis of the coil, said projecting ends of the coil passing through the wall of the. envelope at points spaced inwardly toward the center from 2n the ends of the envelope, said envelope comprising two parts sealed together, the seal joining said envelope parts lying in a plane between said projecting ends of the coiled tube, and a seal uniting the projecting ends of the tube with the envelope.

3. The method of assembling a vacuum tube structure wherein there is an electrode having a body portion and having transversely extending legs projecting outwardly from the sides of the body portion, said electrode being within a substantially cylindrical vitreous envelope with said legs projecting through the Walls of the envelope, which comprises forming the envelope in two parts, each provided. with an aperture for one of said legs,'passing said'l'egs through said apertures, contacting the parts of the envelope and forming a seal at the line of contact, and thereafter forming a seal between the envelope and the said legs.

FREDERICK S. MCCULLOUGH. 20 

